Method of making hydroxymethylphosphonate, polyurethane foam-forming compositions, polyurethane foam and articles made therefrom

ABSTRACT

A method of making hydroxymethylphosphonate comprising heating paraformaldehyde in a solvent to a desired reaction temperature, wherein the solvent is present in at least an amount necessary to solvate or suspend the paraformaldehyde; adding at least one alkyl phosphite to the heated paraformaldehyde, to provide hydroxymethylphosphonate, the alkyl phosphite being added to the heated paraformaldehyde at a rate which will avoid or inhibit the production of a significant exotherm and resulting high/significant level of acid by-product(s), there being present in the reaction medium at least one hindered amine catalyst in which the nitrogen in the amine is directly bound to a secondary and/or tertiary carbon of an organic group; and, optionally, following the completion of the addition, heating the reaction mixture to an elevated temperature.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of makinghydroxymethylphosphonates, polyurethane foam-forming compositionscontaining the same, polyurethane foam formed from the polyurethanefoam-forming compositions, and polyurethane foam articles madetherefrom.

2. Description of Related Art

Polyurethanes are materials that are suitable for a large number ofdifferent applications in the industrial and private sectors. However,their use presents problems whenever it is involved in areas where thereis a risk of fire. To modify their fire behavior, flame-retarding agentsare usually added to these polyurethane materials. However, the use ofcertain flame-retarding agents has presented environmental concerns.

Phosphorous compounds are highly effective flame-retarding agents forpolyurethane foam, owing to their high phosphorous content and goodstability to hydrolysis; such as, for example, phosphonates.Unfortunately, various phosphonates have various processing problemsassociated with their use. Hydroxyalkylphosphonates have found some useas flame-retarding agents but their use has been severely limited bytheir low purity, and specifically their content of acidic by-products.Further, the formation of hydroxyalkylphosphonates has previously beenconducted very quickly, and in small batches, due to extreme exotherms,which occur in the production of such hydroxyalkylphosphonates, whichexotherms can result in the high acid content. Other attempts to producehydroxyalkylphosphonates have necessitated extremely high reactiontemperatures. Still other attempts to produce hydroxyalkylphosphonateshave resulted in significant byproducts and/or low product yields.Therefore, there is a need for means for makinghydroxyalkylphosphonates, which avoids these quality and processingdifficulties.

BRIEF SUMMARY OF THE INVENTION

There is provided herein a method for making hydroxyalkylphosphonate,specifically, hydroxymethylphosphonate(s), which method can effectivelybe conducted at a rate, which results in a high purity, low acidityproduct. The hydroxymethylphosphonate made by the method herein has asignificantly reduced acidity rendering it significantly advantageous topolyurethane foam applications.

Specifically there is provided herein a method of makinghydroxymethylphosphonate comprising heating paraformaldehyde in asolvent to a desired reaction temperature, wherein the solvent ispresent in at least an amount necessary to solvate or suspend theparaformaldehyde; adding at least one alkyl phosphite to the heatedparaformaldehyde, to provide hydroxymethylphosphonate, the alkylphosphite being added to the heated paraformaldehyde at a rate whichwill avoid or inhibit the production of a significant exotherm and theresulting significant amount (high level) of acid by-product(s), therebeing present in the reaction medium at least one hindered aminecatalyst, e.g., an amine whose nitrogen atom is directly bound to asecondary and/or tertiary carbon of an organic group, e.g., an alkylgroup; and, optionally, following the completion of the addition,heating the reaction mixture to an elevated temperature. It will beunderstood herein that organic moieties can comprise any linear,branched or cyclic, alkyl groups, alkenyl groups, alkynyl groups,aromatic groups, and any of the aforesaid containing a heteroatom, suchas, for example, oxygen, nitrogen, or sulfur, wherein said groups cancontain up to about 18 carbon atoms, preferably up to about 12 carbonatoms and most preferably up to about 10 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION

The inventors herein have unexpectedly discovered that the reaction ofalkyl phosphite, with solvated heated paraformaldehyde, can in fact, beconducted at lower reaction temperatures and/or over an extended periodof time, by slowly adding the alkyl phosphite to the heatedparaformaldehyde, in the presence of a hindered amine catalyst. The useof the generally more costly hindered amine catalyst dramaticallyreduces the quaternization of such catalyst by the alkyl phosphitecomponent, resulting in a higher purity product. The use of unhinderedamines in reactions of dialkyl phosphite and paraformaldehyde haspreviously required the reaction be run at high speed to avoid thequaternization of the catalyst. To achieve this high speed of reactionto avoid catalyst quaternization, and to accommodate for the highcracking temperature of paraformaldehyde, i.e., about 110 degreesCelsius, typically the reaction components were combined at once andreacted at high temperatures, which high temperature reaction results inundesirable by-products and/or acidic by-products. Such a method of theimmediate complete addition of one of the reaction components to theother in the presence of unhindered amine catalyst results in a dramaticreaction exotherm, dramatically limiting the batch size, and causing theresulting product from such a immediate addition to have an unacceptablyhigh level of acidic by-product, e.g., greater than 20 mg KOH/g. The useof hindered amine catalyst in the reaction mixture in which addition ofalkyl phosphite to heated solvated paraformaldehyde occurs, allows for apreviously unexpected lower reaction temperature, and a previouslyunexpected possible slower addition, that avoids an excessive exothermand thus avoids the production of acidic by-products.

It will be understood herein that all ranges herein include allsubranges there between and also any combination of endpoints of saidranges.

It will be understood herein that the expression linear or brancheddivalent alkylene group comprises a saturated linear or branched alkylgroup which has sufficient hydrogen atoms removed therefrom to allow thealkyl group to be divalent.

It will be understood herein that the expression linear or brancheddivalent alkenylene group comprises an alkenyl group which hassufficient hydrogen atoms removed therefrom to allow the alkyl group tobe divalent.

Unless indicated otherwise, all weight percentages herein are based onthe total weight of the reaction components.

All temperatures herein are room temperature unless indicated otherwise.

The hydroxymethylphosphonate can be any hydroxymethylphosphonate, whichis made by the method(s) described herein.

Preferably, the hydroxymethylphosphonate is one or more of the generalformula:

and/or, the general formula:

wherein each R is independently the same or different, linear orbranched alkyl group of from 1 to about 8 carbon atoms, preferably from1 to about 6 carbon atoms, and more preferably from 1 to about 3 carbonatoms, linear or branched alkenyl group of from 2 to about 10 carbonatoms, and more preferably from about 3 to about 8 carbon atoms,cycloalkenyl group of from about 5 to about 10 carbon atoms, and morepreferably from about 5 to about 8 carbon atoms, and, cycloalkyl groupof from about 5 to about 10 carbon atoms, and, more preferably fromabout 5 to about 8 carbon atoms; and R* is a linear or branched divalentalkylene group of from 2 to about 10 carbon atoms, preferably from 3 toabout 8 carbon atoms, linear or branched divalent alkenylene group offrom 2 to about 10 carbon atoms, and more preferably from about 3 toabout 8 carbon atoms, divalent cycloalkenyl group of from about 5 toabout 10 carbon atoms, and more preferably from about 5 to about 8carbon atoms, and divalent cycloalkyl group of from about 5 to about 10carbon atoms, and, more preferably from about 5 to about 8 carbon atoms.More preferably, each R is independently selected from the groupconsisting of methyl, ethyl or propyl. R* preferably is a linear orbranched divalent alkylene group containing from 3 to about 8 carbonatoms such as, for example, propylene, 2-methylpropylene, neopentyleneor 2-butyl-2-ethylpropylene.

Some examples of hydroxymethylphosphonates can include dimethylhydroxymethylphosphonate, diethyl hydroxymethylphosphonate, dipropylhydroxymethylphosphonate, di-isopropyl hydroxymethylphosphonate, methylethyl hydroxymethylphosphonate, methyl propyl hydroxymethylphosphonate,methyl isopropyl hydroxymethylphosphonate, ethyl propylhydroxymethylphosphonate, ethyl isopropyl hydroxymethylphosphonate,propyl isopropyl hydroxymethylphosphonate, dibutylhydroxymethylphosphonate, dioctyl hydroxymethylphosphonate, propylpentyl hydroxymethylphosphonate, dicyclohexyl hydroxymethylphosphonate,hydroxymethylphosphonate, 1,3,2-dioxaphosphorinane,5-methyl-2-(hydroxymethyl), 2-oxide; 1,3,2-dioxaphosphorinane,5,5-dimethyl-2-(hydroxymethyl), 2-oxide; 1,3,2-dioxaphosphorinane,5-ethyl-6-propyl-2-(hydroxymethyl), 2-oxide; 1,3,2-dioxaphosphorinane,5,5-dimethyl-6-isopropyl-2-(hydroxymethyl), 2-oxide;1,3,2-dioxaphosphorinane, 5-butyl-5-ethyl-2-(hydroxymethyl), 2-oxide andcombinations thereof.

The alkyl phosphite herein can be any commercially available alkylphosphite and specifically is an alkyl phosphite of the general formula:

or the general formula:

wherein each R is independently the same or different, linear orbranched alkyl group of from 1 to about 8 carbon atoms, preferably from1 to about 6 carbon atoms, and more preferably from 1 to about 3 carbonatoms, linear or branched alkenyl group of from 2 to about 10 carbonatoms, and more preferably from about 3 to about 8 carbon atoms,cycloalkenyl group of from about 5 to about 10 carbon atoms, and morepreferably from about 5 to about 8 carbon atoms, and, cycloalkyl groupof from about 5 to about 10 carbon atoms, and, more preferably fromabout 5 to about 8 carbon atoms and R* is a linear or branched divalentalkylene group of from 2 to about 10 carbon atoms, preferably from 3 toabout 8 carbon atoms, linear or branched divalent alkenylene group offrom 2 to about 10 carbon atoms, and more preferably from about 3 toabout 8 carbon atoms, divalent cycloalkenyl group of from about 5 toabout 10 carbon atoms, and more preferably from about 5 to about 8carbon atoms, and divalent cycloalkyl group of from about 5 to about 10carbon atoms, and, more preferably from about 5 to about 8 carbon atoms.More preferably, each R is independently selected from the groupconsisting of methyl, ethyl or propyl. R* preferably is a linear orbranched divalent alkylene group containing from 3 to about 8 carbonatoms such as, for example, propylene, 2-methylpropylene, neopentyleneor 2-butyl-2-ethylpropylene. Alkyl phosphite used in the presentinvention can be obtained from Rhodia and/or United Phosphorus.

Some examples of alkyl phosphite are selected from the group consistingof dimethyl phosphite, diethyl phosphite, dipropyl phosphite,di-isopropyl phosphite, methyl ethyl phosphite, methyl propyl phosphite,methyl isopropyl phosphite, ethyl propyl phosphite, ethyl isopropylphosphite, propyl isopropyl phosphite, dibutyl phosphite, dioctylphosphite, propyl pentyl phosphite, dicyclohexyl phosphite andcombinations thereof.

The reaction temperature of the present invention is a temperature thatis lower than that which is needed to effect an equivalent reactionbetween an equivalent alkyl phosphite and paraformaldehyde, but whereinthe reaction occurs in the presence of an unhindered amine catalyst. Theparaformaldehyde is heated to the reaction temperature prior to theaddition of alkyl phosphite. Preferably the reaction temperature is fromabout 25 degrees Celsius to about 75 degrees Celsius, more preferablyfrom about 30 to about 75 degrees Celsius, even more preferably fromabout 35 to about 60 degrees Celsius, even more preferably from about 35to about 55 degrees Celsius, yet even more preferably from about 40degrees to about 55 degrees Celsius, and most preferably from about 45degrees to about 55 degrees Celsius. Other preferable reactiontemperature ranges can be from 35 degrees Celsius to about 65 degreesCelsius or from 30 degrees to about 55 degrees Celsius. In oneembodiment the reaction temperature can be from about 45 degrees Celsiusto about 52 degrees Celsius. Additionally, the reaction temperatureherein can be less than room temperature, for example, from about zerodegrees Celsius to about 75 degrees Celsius and any from zero degreesCelsius to any of the reaction temperature endpoints provided herein,such as from about zero degrees Celsius to about 55 degrees Celsius andcombinations of any of the endpoints listed herein.

The hindered amine catalyst used in the present invention is a tertiaryamine in which the nitrogen in the amine is directly bound to asecondary and/or tertiary carbon of an organic group, e.g., an alkylgroup, such a hindered amine catalyst will contain at least one suchgroup, preferably two, and even three. It will be understood herein thatthe use of the expression secondary and/or tertiary carbon of an organicgroup indicates that at least one organic group which is bound to thenitrogen is a secondary or tertiary organic group, e.g., a secondary ortertiary alkyl group, wherein the central carbon in said secondary ortertiary alkyl group is directly bound to the nitrogen of the amine. Itwill be understood that such an organic group may in one embodimentcontain more than one secondary or tertiary carbon, provided that one ofsaid secondary or tertiary carbons is directly bound to the nitrogen ofthe amine.

Preferably, the hindered amine catalyst is of the general formula:

wherein each R¹, R² and R³ is each independently the same or differentlinear, alkyl group containing from one to about 8 carbon atoms,branched alkyl group containing from 3 to about 8 carbon atoms, linearor branched alkenyl group containing up to about 8 carbon atoms, cyclicalkyl group containing from 5 to about 8 carbon atoms, or an aryl groupcontaining from 6 to about 10 carbon atoms, provided that at least oneof the R¹, R² and R³ groups is directly bonded to the amine nitrogen bya secondary and/or tertiary carbon atom of said R¹, and/or R², and/or R³group. Preferably in the hindered amine catalyst of the above generalformula at least two of the R¹, R² and R³ groups are attached via asecondary and/or tertiary carbon, and more preferably all three of theR¹, R² and R³ groups are attached via a secondary and/or tertiarycarbon. In one non-limiting embodiment herein, each R¹, R² and R³ groupof the above general formula of the hindered amine catalyst isindependently the same or different and is selected from the groupconsisting of methyl, ethyl, propyl, butyl, isopropyl, isobutyl,sec-butyl, tert-butyl, isopentyl, neopentyl, isohexyl, isoheptyl,cyclohexyl and phenyl, provided that at least one of the R¹, R² and R³groups are selected from the group consisting of isopropyl, sec-butyl,tert-butyl, and cyclohexyl. Preferably, at least two of the R¹, R² andR³ groups are selected from the group consisting of isopropyl,sec-butyl, tert-butyl, and cyclohexyl and most preferably, all three ofthe R¹, R² and R³ groups are selected from the group consisting ofisopropyl, sec-butyl, tert-butyl, and cyclohexyl.

Some non-limiting examples of hindered amine catalyst that can be usedherein are those selected from the group consisting oftriisopropylamine, tri(sec-butyl)amine, tricyclohexylamine,diisopropylmethylamine, diisopropylethylamine, diisopropylpropylamine,di(sec-butyl)methylamine, di(sec-butyl)ethylamine,di(sec-butyl)propylamine, dicyclohexylmethylamine,dicyclohexylethylamine, dicyclohexylpropylamine,diisopropylisobutylamine, diisopropyl(sec-butyl)amine,diisopropylcyclohexylamine, diisopropylphenylamine,diisobutylisopropylamine, diisobutyl(sec-butyl)amine,diisobutylcyclohexylamine, di(sec-butyl)isopropylamine,di(sec-butyl)isobutylamine, di(sec-butyl)cyclohexylamine,di(sec-butyl)phenylamine, dicyclohexylisopropylamine,dicyclohexylisobutylamine, dicyclohexyl(sec-butyl)amine,dicyclohexylphenylamine, diphenylisopropylamine,diphenyl(sec-butyl)amine, diphenylcyclohexylamine, and combinationsthereof.

The method of the making hydroxymethylphosphonate herein can compriseheating the paraformaldehyde to the reaction temperature followed byadding the alkyl phosphite thereto, as described herein with respect tothe rate of addition, with solvent and hindered amine catalyst presentin the reaction medium and/or mixture.

The hindered amine catalyst finds its employment in the reaction mixturein any manner that is most expedient; provided the herein described rateof addition of alkyl phosphite to the paraformaldehyde is maintained(e.g., there is no extreme/significant exotherm), preferably, thehindered amine catalyst is combined with the paraformaldehyde before,during, or after heating the paraformaldehyde, most preferably beforesaid heating. In another less preferable embodiment, the hindered aminecatalyst is combined with the alkyl phosphite before or during theaddition to paraformaldehyde. In a preferable embodiment, the hinderedamine catalyst is present in a reaction vessel prior to the addition ofparaformaldehyde thereto. Still further, in another embodiment, thehindered amine catalyst can be combined in part with both the alkylphosphite and paraformaldehyde prior to reaction thereof Similarly, thesolvent can be added to the reaction medium in like manner as describedfor the hindered amine catalyst, alone or in combination with thehindered amine catalyst. Preferably, the solvent is added to theparaformaldehyde or the paraformaldehyde is added to the solvent, priorto or during heating of the paraformaldehyde.

Preferably the solvent can be any solvent which effectively solvates orsuspends (with stirring) the paraformaldehyde component. Effectivesolvation or suspension can vary greatly depending on the solvent andthe amount of paraformaldehyde employed in the method herein.Preferably, effective solvation/suspension can comprise sufficientsolvent to effect solvation/suspension of from 50 weight percent of theparaformaldehyde, based on the total weight of paraformaldehyde, to anamount of solvent that is up to about 100 percent more solvent than isnecessary for the complete dissolution/suspension of the totalparaformaldehyde being employed, said latter percent being based uponthe total amount of solvent necessary to completely solvate/suspend thetotal amount of paraformaldehyde being employed. Preferably, the amountof solvent present will be sufficient to solvate/suspend from about 75weight percent of the paraformaldehyde, up to about 25 percent moresolvent than is necessary to completely solvate/suspend the totalparaformaldehyde being employed. In one embodiment, solvent is used inat least the amount necessary to completely solvate and/or suspend theamount of paraformaldehyde being used.

In one preferable embodiment, the solvent is a hydroxyalkylphosphonate,more preferably a hydroxymethylphosphonate, even more preferably any ofthe hydroxymethylphosphonates described herein, and most preferably aportion of hydroxymethylphosphonate remaining from a previous batchformed from the reaction method described herein, i.e., a heel ofproduct hydroxymethylphosphonate. In one embodiment, thehydroxyalkylphosphonate can be other than that of a heel of a previousbatch. Specifically, the portion of remaining hydroxymethylphosphonatefrom a previous batch which can effectively operate as a solvent for theparaformaldehyde can comprise from about 0.01 weight percent to about 35weight percent, preferably from about 5 weight percent to about 30weight percent, more preferably from about 10 weight percent to about 28weight percent, and most preferably from about 15 weight percent toabout 25 weight percent, said weight percent being based on the totalweight of the product hydroxymethylphosphonate of a previous reactionbatch that remains in situ, or is provided from the previous reactionvessel.

In another embodiment herein, the solvent can be any other solvent otherthan hydroxyalkylphosphonate that can effectively solvate/suspend theparaformaldehyde as described above, such as for example, dry solvents.Some non-limiting examples of solvents can comprise toluene, xylene,cyclohexane, n-heptane, hexane, methyl acetate, ethyl acetate, ethanol,propanol, isopropanol, butanol and combinations thereof.

The alkyl phosphite is added to the heated paraformaldehyde at anyintermittent and/or continuous rate that will avoid or inhibit asignificant/high exotherm which results in a high level of acidby-product(s). Such a rate can be determined by those skilled in the artdepending on the specific parameters of the method being practiced,i.e., depending on the specific components, specific amounts andspecific reactor limitations available, as well as any processingvariables. In one embodiment herein it will be understood that thesignificant/high exotherm is an exotherm that will produce the highlevel/significant amount of acid by-products. In one preferableembodiment, an acid by-product is a quaternized amine salt and/or freeacid. In one embodiment a significant high level amount of acidby-product is any amount greater than about 1 percent by weight, morespecifically greater than about 5 percent by weight, and mostspecifically greater than about 10 percent by weight, said percent byweight being based on the total weight of hydroxyalkylphosphonateproduct.

In one other embodiment of the method herein, the alkyl phosphite isadded to the heated paraformaldehyde at any intermittent and/orcontinuous rate that will produce the reaction product in a puritygreater than 90 percent by weight, more preferably greater than about 95percent by weight, and most preferably greater than about 99 percent byweight, said weight percent being based on the total weight of producthydroxymethylphosphonate. In one embodiment herein the reaction producthydroxyalkylphosphonate is produced in a purity of greater than 90percent by weight, preferably greater than 95 percent by weight and mostpreferably greater than about 99 percent by weight, said percent beingbased on the total weight of reaction product. Such purity is to theexclusion of side-products, specifically, P-III-based side-products,such as trialkyl phosphites. More specifically exclusion of sideproducts is understood to be less than about 10 percent by weight, morepreferably less than about 5 percent by weight and most preferably lessthan about 1 percent by weight of said side-products, said percent byweight being based on the total weight of the hydroxymethylphosphonatereaction product. It is understood that in one embodiment herein that inaddition to the avoidance or inhibition of a significant amount of acidby-product (by controlling the exotherm by the control of the rate ofaddition of the alkyl phosphite to the paraformaldehyde), that the rateand/or order of addition will avoid and/or inhibit the production of theabove recited amounts of side-products. Amounts of side-product inexcess of 10 percent by weight will negatively effect, the quality of,and/or the ability to make, polyurethane foam made from polyurethanefoam-forming compositions containing such side-products.

Preferably, in the method described herein, the method will produce ahydroxymethylphosphonate reaction product wherein the product containsless than about 10 percent by weight of quaternized amine salt and/orfree acid, more preferably less than about 5 percent by weight ofquaternized amine salt and/or free acid, and most preferably less thanabout 1 percent by weight of quaternized amine salt and/or free acidbased on the total weight of the reaction product.

In one embodiment herein the acid by-products can be avoided orinhibited by the above stated rate, in that the chosen rate can bechosen so as to prevent an extreme/significant exotherm in the method,i.e., an exotherm that cannot effectively be controlled by cooling thereaction medium and/or reaction mixture. Preferably the rate can bechosen so that any resulting exotherm, if any, is not so far in excessof the desired reaction temperature that cooling cannot effectivelycontrol it. Effective control comprises maintaining the exotherm at nohigher than about 25 degrees Celsius above the desired reactiontemperature, preferably no higher than about 20 degrees above thedesired reaction temperature, more preferably no higher than about 15degrees above the desired reaction temperature, even more preferably nohigher than about 10 degrees above the reaction temperature and mostpreferably no higher than about 5 degrees above the reactiontemperature. By slow addition of the alkyl phosphite either continuouslyor intermittently, extreme exotherm can be avoided or dramaticallyreduced. Preferably, the addition of alkyl phosphite is continuous.

In one embodiment, the alkyl phosphite is added to the heatedparaformaldehyde at a rate that maintains the reaction temperature atfrom about 30 degrees Celsius to about 75 degrees Celsius, morepreferably any of the reaction temperature ranges described herein.Preferably, the alkyl phosphite is added to the heated paraformaldehydeat a rate that maintains the reaction temperature at from about 30degrees Celsius to about 55 degrees Celsius. Alternate range cancomprise from about 30 to about 65 degrees Celsius, from about 35 toabout 60 degrees Celsius, from about 40 to about 55 degrees Celsius andcombinations of any endpoints of said temperature ranges, e.g., fromabout 30 to about 55 degrees Celsius, and the like.

In one embodiment herein the alkyl phosphite is added to the heatedparaformaldehyde over a period of from about 10 minutes to about 24hours, more preferably from about 15 minutes to about 20 hours, evenmore preferably from about 20 minutes to about 15 hours, yet even morepreferably from about 20 minutes to about 10 hours, yet still even morepreferably from about 30 minutes to about 8 hours and most preferablyfrom about 45 minutes to about 5 hours. Such time period ranges includeall ranges therebetween and any combination of said endpoints. In oneembodiment, the alkyl phosphite is added to the heated paraformaldehydeover a period of from about 10 minutes to about 5 hours.

While the step of using an elevated temperature is not necessary in themethod herein, it can be utilized to force the reaction to completion,i.e., the complete or substantial reaction of any (if any) remainingunreacted components following the completion of the addition. It isunderstood herein that the optional elevated temperature step, ifemployed, will employ a temperature that is in excess of the desiredreaction temperature. Preferably, the elevated temperature can be fromany temperature higher than the chosen reaction temperature up to about85 degrees Celsius. More preferably the elevated temperature is fromabout 55 to about 75 degrees Celsius, even more preferably from about 60to about 75 degrees Celsius, and most preferably from about 65 to about75 degrees Celsius. The elevated reaction temperature can be maintainedfrom about 1 minute to about 5 hours, preferably from about 5 minutes toabout 4 hours, more preferably from about 10 minutes to about 3 hoursand most preferably from about 30 minutes to about 2.5 hours.

While the amount of paraformaldehyde and alkyl phosphite can varydramatically depending on the specific reaction components andconditions, solvent, catalyst, desired reaction temperature, and batchsize, preferably, the amount of paraformaldehyde and alkyl phosphite canexist in equivalent or near equivalent molar amounts. Near equivalentmolar amounts can comprise wherein either the paraformaldehyde or alkylphosphite is present in a molar excess of the other component.Preferably, either the alkyl phosphite or the paraformaldehyde componentcan exist in no more than 10 molar percent excess of the othercomponent, more preferably no more than 5 molar percent excess of theother component, and most preferably no more than 3 molar percent excessof the other component. In one preferable embodiment, theparaformaldehyde can be present in about 1 to about 3 molar percentexcess of the molar amount of alkyl phosphite. The solvent can bepresent in the solvating ranges described above but preferably about 5to about 40 weight percent, more preferably from about 10 to about 30weight percent and most preferably, from about 15 to about 25 weightpercent, said weight percent being based on the total weight of thereaction mixture. The catalyst can be used in amounts of preferably fromabout 0.5 to about 5.0 weight percent, more preferably from about 1.0 toabout 4.0 weight percent, and most preferably from about 2.0 to about3.0 weight percent. Advantageously, the reaction herein can be conductedin a large batch. Preferably, the large batch comprises wherein theamount of reaction product produced comprises from 100 grams up to about75,000 pounds, more preferably from about 1 kilogram up to about 65,000pounds, even more preferably from about 100 kilograms up to about 55,000pounds and most preferably from about 1000 kilograms up to about 50,000pounds. The hydroxymethylphosphonate reaction product herein can beadvantageously utilized in polyurethane foam-forming compositions as aflame-retardant for the polyurethane foam formed therefrom and/or as apolyol component in the polyurethane-foam forming composition. Suchpolyurethane foam-forming compositions, and those described herein, madeusing the hydroxymethylphosphonate made by the method described herein,can be reacted to form polyurethane foams, which foams can be utilizedin the construction and formation of various articles such as furniture,bedding, automotive seat cushions, panel, and pour-in-place and sprayfoam insulation. The hydroxymethylphosphonate reaction product of themethod herein can comprise significantly less acidity than an equivalentmethod that utilizes a non-hindered amine catalyst, e.g., triethylamine,and/or a hydroxyalkylphosphonate solvent, and/or conducts the method ata faster rate than is described herein, and/or at a higher temperaturethan is described herein; preferably, the hydroxymethylphosphonatereaction product of the method herein can comprise at least 5 percentless acidity, more preferably at least 10 percent less acidity, evenmore preferably at least 30 percent less acidity and most preferably atleast 75 percent less acidity than such an equivalent method; such anequivalent method can in addition or alone comprise the simultaneousand/or immediate or substantially immediate complete addition of theparaformaldehyde and alkyl phosphite components. In one embodiment, themethod herein can comprise from about 75 to about 80 percent lessacidity than such an equivalent method. Such an immediate addition cancomprise time periods less than the time periods described for themethod herein. As a result, the polyurethane foam made by reacting thepolyurethane foam-forming composition which comprises thehydroxymethylphosphonate made by the method herein contains such loweracidity as is described above. These lower acidity products areadvantageous in that the use of a high acidity reaction product in foamneutralizes the amine catalysts normally used in making the foampreventing the normal foam-making process. In many cases, foam cannot bemade with these high acidity products. Heretoforehydroxymethylphosphonates made by prior art methods were either not usedin polyurethane foam-forming compositions due to the poor quality offoams made by such prior art methods or such hydroxymethylphosphonatesrequired the extensive additional step of purifying the phosphate esterof any acidity and/or side-products prior to their use in polyurethanefoam forming compositions and the articles made therefrom, where saidpurification step(s) dramatically increase the complexity of makingpolyurethane foams and/or additionally increase the costs of making suchfoams. The present invention avoids these previously required steps andprovides a hydroxymethylphosphonate ester that can be directly used inpolyurethane-foam forming compositions and applications without furtherpurification steps, e.g., distillation.

Preferably the hydroxymethylphosphonate made by the method describedherein has an acidity of less than about 15 mg KOH/g, more preferably,less than about 10 mg KOH/g, even more preferably, less than about 8 mgKOH/g, and most preferably less than about 6 mg KOH/g.

In one embodiment herein, the product hydroxymethylphosphonate can beused in a polyurethane foam-forming composition without furtherpurification. Preferably, the product hydroxymethylphosphonate can beused in a polyurethane foam-forming composition without furtherpurification when the solvent comprises a heel ofhydroxymethylphosphonate from a previous batch as described herein. Theheel of hydroxymethylphosphonate avoids and/or reduces any purificationthat can be necessary or desirable prior to use of thehydroxymethylphosphonate reaction product in polyurethane foam-formingcompositions. If a solvent other than hydroxyalkylphosphonate is usedherein then, preferably, distillation or any other known purificationmethod can be used prior to use in a polyurethane foam-formingcomposition to remove the solvent. Advantageously, the hindered aminecatalyst of the method herein can be utilized as the catalyst in apolyurethane foam-forming composition, which comprises, polyol (or ahydroxyl-containing component), isocyanate and catalyst. Preferably, thehydroxymethylphosphonate reaction product of the method described hereinand the hindered amine catalyst of the method herein can remain in situand be used in the polyurethane foam-forming composition or can betransferred to another reaction vessel where they are used in apolyurethane reaction-forming composition.

Preferably there is provided herein a polyurethane foam-formingcomposition comprising a polyol, an isocyanate, a catalyst and thehydroxymethylphosphonate produced by the method described herein.Alternatively, there is also preferably provided a polyurethanefoam-forming composition comprising a polyol, an isocyanate, and boththe hindered amine catalyst and the product hydroxymethylphosphonate ofthe method described herein. Further there is provided a polyurethanefoam-forming composition comprising an isocyanate, a catalyst and thehydroxymethylphosphonate made by the method herein, wherein thehydroxymethylphosphonate functions as an additional hydroxyl-containingcomponent and/or a flame retardant in the polyurethane foam-formingcomposition.

Although the present invention has been described with reference toparticular means, materials and embodiments, from the foregoingdescription, one skilled in the art can easily ascertain the essentialcharacteristics of the present invention and various changes andmodifications can be made to adapt the various uses and characteristicswithout departing from the spirit and scope of the present invention asdescribed above.

EXAMPLES Example 1 Reaction Procedure Using Diisopropylethylamine as theHindered Amine Catalyst

The reaction heal (2.5 liters; i.e., product) was added to the 20 literreactor vessel, followed by the addition 2480 grams of 95% reagent gradeparaformaldehyde powder (78.5 moles of paraformaldehyde). After heatingthe reaction mixture to 50° C., 225 grams of diisopropylethylamine (303ml, 1.74 moles) were added to the reactor, followed by the slow additionof 10350 grams of diethyl phosphite (9655 ml, 74.9 moles). The diethylphosphite addition was completed at ˜90 grams/minute taking a littleless than 2 hours. The reaction temperature was maintained at 50° C.throughout the addition. After completing the addition, the reactiontemperature was raised to 75° C. and held for 1-2 hours or until all ofthe diethyl phosphite was consumed as indicated by P³¹ NMR. After a 1hour vacuum stripping step on a rotary evaporator to remove anyremaining free amine and filtration through a sintered glass filter toremove any solid particulates, the product diethylhydroxymethylphosphonate was isolated in with an acidity of 6.6 mgKOH/g.

Example 2 Reaction Procedure Using Diisopropylethylamine as the HinderedAmine Catalyst

The reaction heal (50 ml; i.e., product) was added to the 1000 mlreactor vessel, followed by the addition 49.7 grams of 95% reagent gradeparaformaldehyde powder (1.58 moles of paraformaldehyde). After heatingthe reaction mixture to 50° C., 4.5 grams of diisopropylethylamine (6.1ml, 0.035 moles) were added to the reactor, followed by the slowaddition of 207.1 grams of diethyl phosphite (193.2 ml, 1.50 moles). Thediethyl phosphite addition was completed in 1.5 hours at a rate of 2.3grams/minute. The reaction temperature was maintained at 50° C.throughout the addition. After completing the addition, the reactiontemperature was raised to 75° C. and held for 1-2 hours or until all ofthe diethyl phosphite was consumed as indicated by P³¹ NMR. After a 1hour vacuum stripping step on a rotary evaporator to remove anyremaining free amine and filtration through a sintered glass filter toremove any solid particulates, the product diethylhydroxymethylphosphonate was isolated in with an acidity of 6.7 mgKOH/g.

Example 3 Reaction Procedure Using Diisopropylethylamine as the HinderedAmine Catalyst, with Alkyl Phosphite Addition at 35° C.

The reaction heal (50 ml; i.e., product) was added to the 1000 mlreactor vessel, followed by the addition 49.7 grams of 95% reagent gradeparaformaldehyde powder (1.58 moles of paraformaldehyde). After heatingthe reaction mixture to 35° C., 4.5 grams of diisopropylethylamine (6.1ml, 0.035 moles) were added to the reactor, followed by the slowaddition of 207.1 grams of diethyl phosphite (193.2 ml, 1.50 moles). Thediethyl phosphite addition was completed in 1.5 hours at a rate of 2.3grams/minute. The reaction temperature was maintained at 35° C.throughout the addition. After completing the addition, the reactiontemperature was raised to 75° C. and held for 1-2 hours or until all ofthe diethyl phosphite was consumed as indicated by P³¹ NMR. After a1-hour vacuum stripping step on a rotary evaporator to remove anyremaining free amine and filtration through a sintered glass filter toremove any solid particulates, the product diethylhydroxymethylphosphonate was isolated in with an acidity of 5.2 mgKOH/g.

Comparative Example 1 Reaction Procedure Using Triethylamine as theAmine Catalyst

Diethyl phosphite (207.1 grams, 193.2 ml, 1.50 moles), 49.7 grams of 95%reagent grade paraformaldehyde powder (1.58 moles of paraformaldehyde)and 5.6 grams of triethylamine (7.7 ml, 0.055 moles) were added to a1000 ml round bottom flask at room temperature with a reflux columnattached. The reaction mixture was heated to 30-40° C. or until thereaction mixture began to exotherm. The temperature of the reactionmixture reached a maximum of 170° C. in 1-2 minutes. Once the exothermsubsided, the reaction mixture was cooled with stirring to roomtemperature. After a 1-hour vacuum stripping step on a rotary evaporatorto remove any remaining free amine and filtration through a sinteredglass filter to remove any solid particulates, the product diethylhydroxymethylphosphonate was isolated with an acidity of 29.0 mg KOH/g.

Comparative Example 2

Reaction procedure using diisopropylethylamine as the hindered aminecatalyst (with addition of paraformaldehyde to phosphite) The use of theterm “comparative” in the title of this example is directed to themethod of adding paraformaldehyde to phosphite, and is not directed tothe use of the diisopropylethylamine catalyst.

Diethyl phosphite (207.1 grams, 193.2 ml, 1.50 moles) and 4.5 grams ofdiisopropylethylamine (6.1 ml, 0.035 moles) were added to a 1000 mlround bottom flask at room temperature with a reflux column attached.After heating the reaction mixture to 50° C., the paraformaldehyde solid(49.7 grams of 95% reagent grade paraformaldehyde powder; 1.58 moles ofparaformaldehyde) was added to the reaction mixture over a period of 1hour (making sure to control the mildly exothermic reaction withcooling) at a rate of ˜0.83 grams/minute. Once the addition wascomplete, the reaction mixture was heated to 75° C. for an additional 2hours. Upon initial heat-up, an exothermic reaction did take placebetween the remaining paraformaldehyde and diethyl phosphite and had tobe cooled to maintain the desired reaction temperature. After completingthe post reaction for 2 hours at 75° C., the reaction mixture wascooled, placed on a rotary evaporator for 1 hour to remove any remainingfree amine and filtered through a sintered glass filter to remove anysolid particulates. The product was isolated with an acidity of 4.7 mgKOH/g. Analysis by P³¹ NMR showed an impure reaction product containing10% by weight of P(III)-based sideproducts, wherein said %(percent) byweight is based on the weight of the hydroxymethylphosphonate reactionproduct.

Comparative Example 3

Exothermic reaction procedure using diisopropylethylamine as the aminecatalyst and involving the immediate addition of all alkyl phosphite andparaformaldehyde to the reaction mixture. The use of the term“comparative” in the title of this example is limited to the immediateaddition of all alkyl phosphite and paraformaldehyde as compared to theslow addition in the above Examples 1-3 and is not directed to the useof the diisopropylethylamine catalyst.

Diethyl phosphite (207.1 grams, 193.2 ml, 1.50 moles), 49.7 grams of 95%reagent grade paraformaldehyde powder (1.58 moles of paraformaldehyde)and 4.5 grams of diisopropylethylamine (6.1 ml, 0.035 moles) were addedto a 1000 ml round bottom flask at room temperature with a reflux columnattached. The reaction mixture was heated to 70-80° C. or until thereaction mixture began to exotherm. The temperature of the reactionmixture reached a maximum of 170° C. in 1-2 minutes. Once the exothermsubsided, the reaction mixture was cooled with stirring to roomtemperature. After a 1-hour vacuum stripping step on a rotary evaporatorto remove any remaining free amine and filtration through a sinteredglass filter to remove any solid particulates, the product diethylhydroxymethylphosphonate was isolated with an acidity of 12.1 mg KOH/g.

1. Hydroxymethylphosphonate produced by the method comprising heatingparaformaldehyde in a solvent to a desired reaction temperature, whereinthe solvent is present in at least an amount necessary to solvate orsuspend the paraformaldehyde; adding at least one alkyl phosphite to theheated paraformaldehyde, to provide hydroxymethylphosphonate, the alkylphosphite being added to the heated paraformaldehyde at a rate whichwill provide the hydroxymethylphosphonate accompanied by acidby-products the total acidity of which is less than about 15 mg KOH/g,there being present in the reaction medium at least one hindered aminecatalyst; and, optionally, following the completion of the addition,heating the reaction mixture to an elevated temperature.
 2. Thehydroxymethylphosphonate of claim 1 wherein the total acidity of theby-products is less than about 10 mg KOH/g.
 3. Thehydroxymethylphosphonate of claim 1 wherein the hydroxymethylphosphonatehas an acidity, the acidity being less than 8 mg KOH/g.
 4. Thehydroxymethylphosphonate of claim 1 wherein the solvent ishydroxyalkylphosphonate in the method by which it is produced.
 5. Thehydroxymethylphosphonate of claim 1 wherein the hydroxymethylphosphonateis of the general formula:

or, the general formula:

in the method by which it is produced, wherein each R is independentlythe same or different, linear or branched alkyl group of from 1 to about8 carbon atoms, linear or branched alkenyl group of from 2 to about 10carbon atoms, cycloalkenyl group of from about 5 to about 10 carbonatoms, and cycloalkyl group of from about 5 to about 10 carbon atoms;and R* is a divalent linear or branched alkylene group of from 2 toabout 10 carbon atoms, linear or branched divalent alkenylene group offrom 2 to about 10 carbon atoms, divalent cycloalkenyl group of fromabout 5 to about 10 carbon atoms, and divalent cycloalkyl group of fromabout 5 to about 10 carbon atoms.
 6. The hydroxymethylphosphonate ofclaim 1 wherein the alkyl phosphite is of the general formula:

or the general formula:

in the method by which it is produced, wherein each R is independentlythe same or different, linear or branched alkyl of from 1 to about 8carbon atoms, linear or branched alkenyl group of from 2 to about 10carbon atoms, cycloalkenyl group of from about 5 to about 10 carbonatoms, and, cycloalkyl group of from about 5 to about 10 carbon atoms;and R* is a linear or branched divalent alkylene group of from 2 toabout 10 carbon atoms, linear or branched divalent alkenylene group offrom 2 to about 10 carbon atoms, divalent cycloalkenyl group of fromabout 5 to about 10 carbon atoms, and divalent cycloalkyl group of fromabout 5 to about 10 carbon atoms.
 7. The hydroxymethylphosphonate ofclaim 1 wherein the reaction temperature in the method by which it isproduced is from about 30 degrees Celsius to about 75 degrees Celsius.8. The hydroxymethylphosphonate of claim 1 wherein the reactiontemperature in the method by which it is produced is from about 35degrees Celsius to about 60 degrees Celsius.
 9. Thehydroxymethylphosphonate of claim 1 wherein the reaction temperature inthe method by which it is produced is from about 35 degrees Celsius toabout 55 degrees Celsius.
 10. The hydroxymethylphosphonate of claim 1wherein the hindered amine catalyst in the method by which it isproduced is a tertiary amine in which the nitrogen in the amine isdirectly bound to a secondary and/or tertiary carbon of an organicgroup.
 11. The hydroxymethylphosphonate of claim 1 wherein the hinderedamine catalyst in the method by which it is produced is of the generalformula:

wherein each R¹, R² and R³ is each independently the same or differentlinear alkyl group containing from one to about 8 carbon atoms, branchedalkyl group containing from 3 to about 8 carbon atoms, linear orbranched alkenyl group containing up to about 8 carbon atoms, cyclicalkyl group containing from 5 to about 8 carbon atoms, or an aryl groupcontaining from 6 to about 10 carbon atoms, provided that at least oneof the R¹, R² and R³ groups are bonded to the nitrogen via a secondaryor tertiary carbon of the R¹, and/or R² and/or R³ group.
 12. Thehydroxymethylphosphonate of claim 11 wherein each R¹, R² and R³ group isindependently the same or different and is selected from the groupconsisting of methyl, ethyl, propyl, butyl, isopropyl, isobutyl,sec-butyl, tert-butyl, isopentyl, neopentyl, isohexyl, isoheptyl,cyclohexyl and phenyl, provided that at least one of the R¹, R² and R³groups are selected from the group consisting of isopropyl, sec-butyl,tert-butyl, and cyclohexyl.
 13. The hydroxymethylphosphonate of claim 1wherein the hindered amine catalyst in the method by which it isproduced is selected from the group consisting of triisopropylamine,tri(sec-butyl)amine, tricyclohexylamine, diisopropylmethylamine,diisopropylethylamine, diisopropylpropylamine, di(sec-butyl)methylamine,di(sec-butyl)ethylamine, di(sec-butyl)propylamine,dicyclohexylmethylamine, dicyclohexylethylamine,dicyclohexylpropylamine, diisopropylisobutylamine,diisopropyl(sec-butyl)amine, diisopropylcyclohexylamine,diisopropylphenylamine, diisobutylisopropylamine,diisobutyl(sec-butyl)amine, diisobutylcyclohexylamine,di(sec-butyl)isopropylamine, di(sec-butyl)isobutylamine,di(sec-butyl)cyclohexylamine, di(sec-butyl)phenylamine,dicyclohexylisopropylamine, dicyclohexylisobutylamine,dicyclohexyl(sec-butyl)amine, dicyclohexylphenylamine,diphenylisopropylamine, diphenyl(sec-butyl)amine,diphenylcyclohexylamine, and combinations thereof.
 14. Thehydroxymethylphosphonate of claim 1 wherein the alkyl phosphite in themethod by which it is produced is added to the heated paraformaldehydeat a rate that maintains the reaction temperature at from about 30degrees Celsius to about 75 degrees Celsius.
 15. Thehydroxymethylphosphonate of claim 1 wherein the alkyl phosphite in themethod by which it is produced is added to the heated paraformaldehydeat a rate that maintains the reaction temperature at from about 30degrees Celsius to about 55 degrees Celsius.
 16. Thehydroxymethylphosphonate of claim 1 wherein the alkyl phosphite in themethod by which it is produced is added to the heated paraformaldehydeover a period of from about 10 minutes to about 24 hours.
 17. Thehydroxymethylphosphonate of claim 1 wherein the alkyl phosphite in themethod by which it is produced is added to the paraformaldehyde over aperiod of from about 10 minutes up to about 5 hours.
 18. Thehydroxymethylphosphonate of claim 1 wherein the elevated temperature inthe method by which it is produced is sufficient to complete thereaction of any unreacted components.
 19. The methodhydroxymethylphosphonate of claim 1 wherein, in the method by which itis produced, the product contains less than about 10 percent by weightof quaternized amine salt and/or free acid.
 20. Thehydroxymethylphosphonate of claim 1 wherein, in the method by which itis produced, the product contains less than about 5 percent by weight ofquaternized amine salt and/or free acid.
 21. Thehydroxymethylphosphonate of claim 1 wherein, in the method by which itis produced, the product hydroxymethylphosphonate has a purity ofgreater than 90 percent by weight.
 22. The hydroxymethylphosphonate ofclaim 1 wherein, in the method by which it is produced, the reactionmixture contains less than 10 percent by weight of P-III side-productsbased on the weight of the hydroxymethylphosphonate.
 23. Thehydroxymethylphosphonate of claim 1 wherein the producthydroxymethylphosphonate can be used in a polyurethane foam-formingcomposition without further purification.
 24. Thehydroxymethylphosphonate of claim 1 wherein, in the method by which itis produced, the reaction is conducted in a large batch.